The recent resurgence of populism poses a significant challenge to constitutional law today and to the deeper tradition of modern constitutionalism. Despite resisting formal limitations on their power to represent the ‘true’ popular will, populist regimes nevertheless find instrumental and ideological reasons to endorse their own version of constitutionalism. And despite their nativist commitments, populist leaders across the globe find common constitutional cause and mutual encouragement in their critique of cosmopolitan institutions and values. The distinctiveness of populism’s constitutional orientation rests on its occupation of a space between authoritarian and popular versions of constitutionalism, overlapping both but not reducible to either. There situated, populism involves a reaction against what it condemns as the neglect of the unitary collective particular in the liberal version of modern constitutionalism. Many critical of the inflated narratives and methods of populism nevertheless share some its underlying anxieties. For in an age in which an expanding commitment to the democratic pedigree of our constitutional arrangements has unfolded alongside the increasing transnationalization and fragmentation of political authority, the very instability of the balance between various constitutional goods – between individualism and collectivism, universal and particular rationalities, and plurality and unity – that fuels populists’ ire, deepens the defining tension of modern constitutionalism and poses a challenge to all who continue to endorse it.